Apparatus for sterilizing an instrument channel of a surgical scoping device

ABSTRACT

Sterilization apparatus comprising a sterilization instrument configured to be inserted through the instrument channel of a surgical scoping device and a withdrawal device for withdrawing the sterilization instrument from the instrument channel at a predetermined rate. The sterilization instrument comprises an elongate probe having a probe tip with a first electrode and a second electrode arranged to produce an electric field from received RF and/or microwave frequency EM energy. In operation the instrument may disinfect an inner surface of the instrument channel by emitting energy whilst being withdrawn through the channel.

FIELD OF THE INVENTION

The present invention relates to sterilization of surgical scopingdevices such as endoscopes. In particular, the invention relates to anapparatus which can be used to sterilize or disinfect the instrumentchannels of such surgical scoping devices.

BACKGROUND OF THE INVENTION

Bacteria are single-celled organisms that are found almost everywhere,exist in large numbers and are capable of dividing and multiplyingrapidly. Most bacteria are harmless, but there are three harmful groups;namely: cocci, spirilla, and bacilla. The cocci bacteria are roundcells, the spirilla bacteria are coil-shaped cells, and the bacillibacteria are rod-shaped. The harmful bacteria cause diseases such astetanus and typhoid.

Viruses can only live and multiply by taking over other cells, i.e. theycannot survive on their own. Viruses cause diseases such as colds, flu,mumps and AIDS. Fungal spores and tiny organisms called protozoa cancause illness.

Such micro-organisms are known to persist in the instrument channel ofsurgical scopes (such as endoscopes, gastroscopes etc.), and it isdesirable to remove these organisms. Sterilization is an act or processthat destroys or eliminates all form of life, especiallymicro-organisms.

Known methods of sterilizing the instrument channels of scopes involvethe use cleaning fluids which are flushed through the channel to expeldebris. A brush may also be used to scrub the interior. The scope isthen disinfected in automatic washing or disinfection units, which mayinvolve the immersion of the scope in potentially harmful chemicals suchas glutaraldehyde. Finally, the scope is rinsed thoroughly with water,then alcohol, to remove traces of the disinfectant.

Such known methods are labor-intensive, and are also prone to incompleteor insufficient sterilization of the instrument channel. The presentinvention aims to address these issues.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is providedsterilization apparatus for sterilizing an instrument channel of a scopedevice. The apparatus comprises a sterilization instrument configured tobe inserted through the instrument channel of a surgical scoping device(also referred to herein as simply a “scoping device”) and a withdrawaldevice for withdrawing the sterilization instrument from the instrumentchannel at a predetermined rate. The sterilization instrument comprisesan elongate probe comprising a coaxial cable for conveyingradiofrequency (RF) and/or microwave frequency electromagnetic (EM)energy, and a probe tip connected at the distal end of the coaxial cablefor receiving the RF and/or microwave energy. The coaxial cablecomprises an inner conductor, an outer conductor, and a dielectricmaterial separating the inner conductor from the outer conductor. Theprobe tip comprises a first electrode connected to the inner conductorof the coaxial cable, and a second electrode connected to the outerconductor of the coaxial cable, wherein the first electrode and secondelectrode are arranged to produce an electric field from the received RFand/or microwave frequency EM energy.

In this way, the first aspect of the invention provides the ability toperform sterilization at the distal end of an instrument, in particularfor the purpose of disinfecting the instrument channel of surgicalscoping device, such as an endoscope, gastroscope, bronchoscope or thelike. The apparatus allows the instrument channel to be thoroughlysterilised using RF and/or microwave frequency EM energy, which issupplied to the probe tip from a generator.

The term “surgical scoping device” may be used herein to mean anysurgical device provided with an insertion tube that is a rigid orflexible (e.g. steerable) conduit that is introduced into a patient'sbody during an invasive procedure. The insertion tube may include theinstrument channel and an optical channel (e.g. for transmitting lightto illuminate and/or capture images of a treatment site at the distalend of the insertion tube. The instrument channel may have a diametersuitable for receiving invasive surgical tools. The diameter of theinstrument channel may be 5 mm or less.

In this specification “microwave frequency” may be used broadly toindicate a frequency range of 400 MHz to 100 GHz, but preferably therange 1 GHz to 60 GHz. Specific frequencies that have been consideredare: 915 MHz, 2.45 GHz, 3.3 GHz, 5.8 GHz, 10 GHz, 14.5 GHz and 24 GHz.In contrast, this specification uses “radiofrequency” or “RF” toindicate a frequency range that is at least three orders of magnitudelower, e.g. up to 300 MHz, preferably 10kHz to 1 MHz. The microwavefrequency may be adjusted to enable the microwave energy delivered to beoptimised. For example, a probe tip may be designed to operate at acertain frequency (e.g. 900 MHz), but in use the most efficientfrequency may be different (e.g. 866 MHz).

The elongate probe may be dimensioned to be insertable through a scopingdevice, e.g. through the instrument channel of an endoscope,gastroscope, bronchoscope, colonoscope or the like. For example, thecoaxial cable may have a diameter of 2.5 mm or less, preferably 2.2 mmor less. The coaxial cable may have a sleeve, wherein the sleeve mayhave an outer diameter less than 2.6 mm, preferably less than 2.5 mm.For larger laparoscopic instruments, the outer diameter may be 3 mm ormore, and larger diameter co-axial cable may be used. The coaxial cablemay have a length of around 2 m or more to ensure that the probe canextend through the entire length of the instrument channel. For example,in colonoscopes, the instrument channel may be around 1.8 m in length.The first electrode may be a radiating microwave monopole antennastructure coupled to receive RF and/or microwave EM energy from thecoaxial cable. The outer conductor of the coaxial cable may be groundedto form an unbalanced feed or may be floating to form a balanced feed tothe antenna, i.e. where the voltage on both conductors is going up anddown.

Preferably the first electrode is shaped to act as a microwave antennafor emitting a microwave field corresponding to the received microwaveEM radiation.

Herein, the term “inner” means radially closer to the center (e.g. axis)of the instrument channel and/or coaxial cable. The term “outer” meansradially further from the center (axis) of the instrument channel and/orcoaxial cable. The term “conductive” is used herein to mean electricallyconductive, unless the context dictates otherwise. Herein, the terms“proximal” and “distal” refer to the ends of the elongate probe. In usethe proximal end is closer to a generator for providing the RF and/ormicrowave energy, whereas the distal end is further from the generator.

Preferably the sterilization instrument further comprises a gas conduitfor conveying gas to the probe tip, wherein the first electrode andsecond electrode may be arranged to produce an electric field from thereceived RF and/or microwave frequency EM energy across a flow path ofgas received from the gas conduit to produce a thermal or non-thermalplasma. The thermal or non-thermal plasma may be used to provide areduction in bioburden for a range of bacteria, includingmethicillin-resistant staphylococcus aureus (MRSA), clostridiumdifficile (c. diff.; both spores and vegetative state) and escherichiacoli (e. coli), and so may allow for more efficient and thoroughsterilization of the instrument channel. The instrument may also beconfigured to produce a combination of non-thermal plasma andnon-ionising microwave radiation.

In some embodiments the coaxial cable has a lumen extending from aproximal end to a distal end of the cable, wherein the lumen may formthe gas conduit for conveying gas through the elongate probe to theprobe tip. Such arrangements may make the sterilization instrument morecompact, such that energy and gas may be conveyed down the sterilizationinstrument to the probe tip independently of any control line or feedline that runs through the instrument channel. Accordingly, thesearrangements may increase the space available for additional supplies orcomponents (e.g. control wires) to be used with the sterilizationinstrument. Moreover, these arrangements may reduce or eliminate theeffect that additional supplies or components have on energy conveyed bythe coaxial cable.

The gas conduit may have an input port located at a proximal end of thesterilization instrument for connecting to a source of gas (e.g. apressurised gas canister or the like). The gases that are of interestfor implementation of the apparatus disclosed herein are: air, helium,argon, nitrogen, compressed air, and carbon dioxide. The system need notbe limited to these gases. Gas mixtures may be used, e.g. variousconcentration of argon, air and helium may be used, e.g. 1% air and 99%helium, or 5% air and 95% helium. To provide directivity to the gasfeed, compressed air may be used.

The apparatus may include a flow controller arranged to adjustablycontrol gas flow in the gas conduit. The gas flow rate may affect thesize of the plasma plume or the plasma energy; this may be controlled bythe flow controller. Preferably the gas conduit passes through the probetip. This may aid the generation of plasma in the vicinity of the firstand second electrodes at the probe tip. In some embodiments, the gasconduit may be arranged to ensure that the plasma plume extends outsidethe probe tip to contact the surface to be sterilised.

The plasma may be struck using RF or microwave energy, which may bereceived as a high voltage pulse. Microwave energy may be used tosustain the plasma after it is struck, i.e. deliver power into theplasma to maintain the state of ionization. This may also be received asa pulse. This arrangement may prevent electric field collapse due to thecapacitance of the cable and loading variations, e.g. due to changingfrom a dry to a wet environment at the probe tip. Striking the plasmafor delivery out of the probe tip using microwave frequency energy maybe possible, e.g. by using a microwave resonator or an impedancetransformer, i.e. a quarter wave transformer that transforms a lowvoltage to a higher voltage to strike plasma using a higher impedancetransmission line that is a quarter wave (or an odd multiple thereof)long at the frequency of operation. This high impedance line may beswitched in to strike plasma and switched out (i.e. to return to a lowerimpedance line) once the plasma has been struck and it is required tosustain plasma. A power PIN or varactor diode may be preferably used toswitch between the two states, although it may be possible to use acoaxial or waveguide switch. The high electric field for striking theplasma may be caused by creating a high impedance condition for eitherthe RF EM energy or the microwave EM energy at the probe tip. This canbe achieved through the selection of a suitable geometry for the firstand second electrodes. For example, a piece of insulating dielectricmaterial, such as quartz or other similarly low loss material, may belocated between the first and second electrodes. This may increase theimpedance and therefore facilitate the creation of a high electricfield.

To strike plasma it is desirable to have a high electric field (e.g.high voltage condition). In the plasma strike state (i.e. before theplasma exists) the gas is non-conducting and therefore has highimpedance. In order to strike plasma, it is necessary to set-up the highimpedance state at the distal end of the probe tip or within the probetip in order to enable the high voltage (high electric field) necessaryto break down the gas to be generated. The apparatus of the inventionmay permit the magnitude of microwave power delivered to the plasma tobe controlled, e.g. through modulation of the microwave signal andcontrol of amplifier gain or control of the level of input signal to anamplifier with fixed gain, as well as the efficiency by which it isdelivered, e.g. through dynamic impedance matching. This arrangement mayalso enable the dosage of plasma energy delivered into the surface to besterilised to be accurately quantified.

The impedance of the plasma is preferably matched to the impedance ofthe probe tip (and energy delivery system) at the frequency of themicrowave energy to enable efficient transfer of the microwave energy,produced by the generator, into the plasma. Where microwave energy isused, the probe tip and/or generator may be tuned (statically ordynamically) to ensure that the plasma is matched into the loadpresented by the instrument channel and material within the channel. Atmicrowave frequencies, the coaxial cable forms a distributed elementtransmission line, where the impedance match between the probe tip andenergy source is determined by the source impedance of the microwavegenerator, the characteristic impedance of the coaxial cable(transmission line), and the impedance of the probe tip structureitself. If the characteristic impedance of the coaxial cable is the sameas the output impedance of the source then all of the microwave powerwill be delivered into the probe tip, less the attenuation caused by thecoaxial cable (dielectric and conductor losses). If the impedance of theprobe tip and the instrument channel is the same as the characteristicimpedance of the coaxial cable, then the maximum power available at thesource will be transferred into the plasma/instrument channel load.Adjustments may be made to probe tip structure in order to maintain thebest impedance match between the probe tip and the plasma/instrumentchannel load, as explained below. Adjustments may also be made at thegenerator or at the interface between the distal end of the first cableand the proximal end of the second (instrument) cable. These adjustmentsmay be in the form of a change of capacitance and/or inductance of amatching network, i.e. stub tuning.

The apparatus may use, as a generator, a source oscillator to produce alow power microwave frequency signal and a power amplifier (e.g. anarrangement of microwave transistors) to amplify the low power signal toa level that is high enough to enable an electric field to be producedwhich is required to strike the plasma using a gas found to be suitablefor the particular application. Solid state signal amplifiers may beused. The system may also operate in a mode whereby the amplifier isdriven into saturation or full power to set up an electric fieldnecessary to strike the plasma and then backed off once it has beenstruck. The ability to control the microwave energy can enable a plasmato be generated that is most suitable for any one of a variety ofapplications of interest. Control of the microwave energy and/or the gasflow rate and/or the gas mixture gives control over the size of theplume and the temperature at the inner surface of the instrument channelbeing treated. Furthermore, the system may be arranged to quantify thedosage of plasma energy delivered to the surface to be treated. Themicrowave energy may be controlled by any one or more of varying afrequency of the microwave energy in a controlled manner (e.g.controlling the frequency of radiation from the microwave radiationgenerator), varying the power level in a controlled manner, andmodulating the microwave energy in a controlled manner. The generatormay include a microwave signal modulator arranged to modulate themicrowave energy delivered to the probe tip. The modulation frequencymay be contained within the range from 0.1 Hz up to 10 MHz. The dutycycle may be from less than 1% to 100%. In some embodiments, themodulation frequency may be from 10 Hz to 100 kHz and the duty cycle maybe between 10% and 25%. In preferred embodiments the modulationfrequency may be between 100 Hz and 1 kHz, and the duty cycle may be20%.

The apparatus may thus be arranged to generate the plasma using pulsedoperation. In one embodiment, the plasma may be struck on each pulse(the strike may occur due to a transient produced on one of the edges ofthe pulse—normally the positive going edge). The operation of the systemmay be such that it is necessary to keep applying pulses to the systemin order to generate the required effects.

In some embodiments, the probe tip may be a plasma applicator having anenclosed plasma generating region and an outlet for directing plasma outof the plasma generating region towards an inner surface of theinstrument channel. The plasma applicator may direct and/or focus theplasma using suitable antenna arrangements that are designed anddeveloped specifically to enable a suitable plume of plasma, or aplurality of plumes, to be created and delivered in such a manner thatcontrolled thermal/non-thermal plasma may be produced that is useful fordestroying various types of bacteria or viruses or fungi. In oneembodiment, the plasma applicator may be arranged selectively to emitplasma (ionising radiation) and microwave (non-ionising) radiation. Theapparatus may thus emit plasma only, microwave energy only, or a mix ofthe two.

Coaxial arrangements may be used as applicators to create the plasma.For example, a plasma applicator may comprise a coaxial assembly havingan inner conductor surrounded by and separated from an outer conductor,wherein the inner conductor tapers at its distal end to concentrate anelectric field in the plasma generating region to promote strikingplasma when gas and microwave energy are delivered thereto. The coaxialassembly may include a plurality of voltage transformers each havingdifferent impedance, the plurality of voltage transformers beingarranged to concentrate an electric field in the plasma generatingregion. Each voltage transformer may comprise a section of the coaxialassembly having a length that is a quarter wavelength of the microwaveenergy carried thereby from the microwave generator and wherein theimpedances of the plurality of voltage transformers can be set byselecting the outer diameter of the inner conductor in each section ofthe coaxial assembly.

Quarter wave (or an odd number thereof) impedance transformers may berealised in coaxial or waveguide systems and the specific structure usedmay be determined by the specific application and the environment inwhich it is desired to generate the plasma. In one embodiment, thesystem may comprise a solid state source, a tuner and simple fixedimpedance (e.g. 50Ω) applicator structure to create and sustain plasma.In another embodiment, the system may not include a tuner, but may havea voltage transformer in the applicator (created e.g. using a pluralityof impedance transformers) to strike the plasma and then keep strikingto create a quasi-continuous plasma. Repeated plasma strikes may bebeneficial to regulating the plasma temperature. To create the plasma,the plasma applicator may include igniters which may be made fromceramic/intermetallic material or piezo-igniters which generate a highvoltage spark based on the impact of a spring driven hammer arrangementon the piezoelectric ceramic material. Once the plasma has been struck,or initiated, the microwave energy may then be used to enable the plasmato be sustained or maintained. Tuning elements within the instrument orwithin the generator may be used to facilitate this.

The plasma applicator may include one or more resonator structures madefrom tungsten or another material that can withstand high temperatures.For example, the resonant structure may include a tungsten rod or needlecoated with a material that is a good conductor, i.e. silver, copper orgold. As an example, silver nitrate may be used to electroplate theneedle with silver or copper sulphate used to coat with copper. Otherlow loss conductors may be used, e.g. copper, aluminum, silver coatedstainless steel, etc., which have a small length of tungsten crimped tothe distal end where the plasma is to be generated. Quartz tubes orquartz slices may be used inside the structure for the purpose ofintensifying the electric field generated between the inner and outerelectrode in a coaxial applicator arrangement by effectively bringingthe two conductors closer together. The quartz tube also prevents arcingbetween the two conductors, which helps to produce a uniform beam ofplasma. It is preferable to use a low loss quartz material.

The plasma applicator may include sensing means at its distal end whichis arranged to provide information concerning the plasma to enableadjustments (if needed) to take place, i.e. spectral content(wavelengths), plasma energy and plasma temperature. For example, theplasma applicator may include any of a temperature sensor, acalorimeter, one or more photo detectors for monitoring a spectralcontent of the plasma produced at the distal end of the applicator. Theinformation obtained from these sensors may be used in a feedback loopto control the plasma produced at the output of the system, i.e. controlthe microwave power level, the duty cycle, the waveform of the microwavepower, the gas flow rate, the gas mixture, the gas timing, etc.

In some embodiments, where the probe tip is a plasma applicator, a DCfield or DC voltage level may be applied to the microwave field in theplasma generating region. In a particular arrangement, a bias ‘T’ may beused at the input to the plasma applicator or the antenna and the DCvoltage applied through an inductor, whereas the microwave field may beapplied through a capacitor. In this arrangement, the inductor will passthe DC voltage but block the high frequency microwave signal. Theinductive reactance is given by 2nfL (where f is the frequency of themicrowave energy and L is the inductance of the inductor). If thefrequency is zero (i.e. DC), and inductance has a finite value, theimpedance tends to zero. The capacitor will pass the high frequencymicrowave signal but block the DC voltage. The capacitive reactance isgiven by 1/(2nfC) (where C is the capacitance of the capacitor). If thefrequency tends to infinity (e.g. 400 MHz or more) and the capacitancehas a finite value, the impedance tends to zero. The DC voltage may beused to initiate or strike the plasma and the microwave field may beused to sustain the plasma. A fixed tuning stub or a plurality of tuningstubs may also be arranged as a band reject filter to replace theinductor and be used to block or stop the high frequency signals gettingback into the low frequency or DC generator.

In some embodiments, the sterilization instrument may also be configuredfor use as an electrosurgical instrument. An electrosurgical instrumentmay be any instrument, or tool, which is used during surgery and whichutilizes RF or microwave energy. This means that the same device whichis used for sterilization of the instrument channel may be used forinvasive or non-invasive electrosurgery such as coagulation (e.g. intreating peptic ulcers or coagulation of large blood vessels), tissueresection, or other open and keyhole or laparoscopic procedures. In thisway, the sterilizing function may also be used to sterilize bodycavities before or after treatment. Further, the sterilizationinstrument may also be configured to produce non-thermal plasma, thermalplasma and non-ionising microwave radiation where it is to be used inNOTES procedures or where it is advantageous to be able to performsurface coagulation, sterilization of body tissue and deep coagulationof large vessels or bleeders.

Preferably, the coaxial cable comprises a layered structure comprising:an innermost insulating layer; an inner conductive layer formed on theinnermost insulating layer; an outer conductive layer formed coaxiallywith the inner conductive layer; and a dielectric layer separating theinner conductive layer and the outer conductive layer, wherein the innerconductive layer, the outer conductive layer and the dielectric layerform a transmission line for conveying RF and/or microwave frequencyenergy, and wherein the innermost insulating layer is hollow to form achannel through the sterilization instrument. The diameter of thechannel formed in the innermost insulating layer is preferably 3 mm orless, e.g. 2.8 mm. The channel may form the gas conduit for conveyinggas to the probe tip.

The layer-structured coaxial cable may include, e.g. at a distal endthereof, a first terminal that is electrically connected to the innerconductive layer and which extends through the innermost insulatinglayer into the channel, and a second terminal that is electricallyconnected to the outer conductive layer and which extends through thedielectric layer and innermost insulating layer into the channel. Thefirst terminal and the second terminal may be arranged to formelectrical connection (e.g. physically engage) corresponding contactsformed on a probe tip that is insertable in or through the channel. Thefirst terminal and the second terminal may be formed at the distal endof the inner conductive layer and outer conductive layer respectively.The outer conductive layer may extend longitudinally further in a distaldirection than the inner conductive layer, whereby the first terminal islocated proximally from the second terminal. In such embodiments, theprobe tip may include a connection collar having a first contact forconnecting to the first terminal and a second contact for connecting tothe second terminal. The first contact and the second contact may beelectrically connected to the first electrode and the second electroderespectively.

The probe tip may be introduced to the distal end of the channel via acatheter that is fed through the channel. A connection collar may bemounted on the catheter, and may comprise a cylindrical body having adiameter greater than the diameter of the catheter. The outer surface ofthe cylindrical body may be in close proximity (e.g. touching) theinnermost layer of the layer-structured coaxial cable, to ensure secureengagement between the first contact and first terminal and between thesecond contact and second terminal. The first terminal and secondterminal may project inwards from the innermost layer slightly. Theconnection collar may include a shoulder for abutting a stop flange atthe distal end of the coaxial cable to securely locate the collar inposition. The probe tip may include an extension sleeve that extendsaxially away from the connection collar. In use, the extension sleevemay thus protrude out of the end of the channel. The extension sleevemay comprise a tube of dielectric material, and may carry conductivestructures (e.g. conductive rods or the like) which provide electricalconnection between the first contact and first electrode and between thesecond contact and second electrode respectively. The conductivestructure may comprise a short length of conventional coaxial cable.

If the probe tip is arranged to receive RF energy from thelayer-structured coaxial cable, it may be desirable to prevent voltagebreakdown from occurring between the inner conductive layer and outerconductive layer. This may be achieved by using a material with a highbreakdown threshold (e.g. Kapton® polyimide tape) as the dielectriclayer. Alternatively, if the probe tip is arranged to receive both RFenergy and microwave energy from the layer-structured coaxial cable, itmay be desirable to create separate pathways for the RF energy andmicrowave energy, because low loss dielectric material suitable forsupporting microwave energy propagation may not have a high enoughbreakdown threshold to safely insulate conductors carrying RF energy.Accordingly, the layer-structured coaxial cable may include anadditional conductor which forms a first pole of an RF-carrying bipolartransmission line, and wherein the inner conductive layer and the outerconductive layer form a second pole of the RF-carrying bipolartransmission line. For example the additional conductor may be aconductive wire carried within the instrument channel. In thisarrangement, the innermost insulating layer may be made of a material(e.g. polyimide) with the required breakdown properties. Where anadditional conductor is provided to carry the RF energy, the innerconductive layer and outer conductive layer of the layer-structuredcoaxial cable may be electrically connected (shorted) at the proximalend thereof.

With an arrangement such as this it may be necessary to provide aconfiguration, such as a diplexer, at the distal end of thelayer-structured coaxial cable to prevent the higher voltageradiofrequency signal from travelling back along the inner conductivelayer and outer conductive layer, and/or to prevent the microwave signalfrom travelling back along the additional conductor.

The dielectric layer may comprise a solid tube of dielectric material ora tube of dielectric material having a porous structure. Being a solidtube of dielectric material may mean that the dielectric material issubstantially homogeneous. Having a porous structure may mean that thedielectric material is substantially inhomogeneous, with a significantnumber or amount of air pockets or voids. For example, a porousstructure may mean a honeycomb structure, a mesh structure, or a foamstructure. The dielectric material may comprise PTFE, or anotherlow-loss microwave dielectric. The dielectric material may comprise atube with a wall thickness of at least 0.2 mm, preferably at least 0.3mm, more preferably at least 0.4 mm, e.g. between 0.3 and 0.6 mm.

The inner conductive layer and/or the outer conductive layer maycomprise: a metal coating on the inside or outside of a tube ofmaterial; a solid tube of metal positioned against the inside or outsideof a tube of material; or a layer of braided conductive materialembedded in a tube of material. The inner conductive layer and/or theouter conductive layer may comprise a silver coating. The innerconductive layer and/or the outer conductive layer may have a thicknessof approximately 0.01 mm.

Instead of being projections, one or both of the first terminal and thesecond terminal may comprise a recess, e.g. formed in the innermostinsulating layer. The connection collar (discussed above) for exampleformed in an end face of the cable, for receiving a correspondingconductive protrusion on an end face of the probe tip.

In one configuration the layer-structured coaxial cable may befabricated as a plurality of layers, e.g. a hollow inner tubular layer(the innermost insulating layer); a layer of conductive material on anouter surface of the hollow inner tubular layer (inner conductivelayer); a tube of dielectric material on an outer surface of theconductive material (dielectric layer; and a layer of conductivematerial on an outer surface of the tube of the dielectric material(outer conductive layer). The structure may, or may not, comprise airgaps between some or all of these layers. An advantage of avoiding airgaps is that losses in the cable may be minimized. In one example, thisstructure could be manufactured by sequentially coating each subsequentlayer over the preceding (inner) layer.

Alternatively, this structure could be made by forming one or more ofthe layers as a first part and one or more of the layers as a secondpart, and then sliding one part inside of the other. The hollow innertubular layer preferably comprises polyimide, but may be PTFE or othersuitable insulating material. The hollow inner tubular layer may have athickness of 0.1mm.

In some embodiments, the probe tip may comprise an extension of theinnermost insulating layer, e.g. an innermost PTFE tube, and the innerconductive wrap of the layer-structured coaxial cable, and the channelmay extend through the probe tip. A dielectric cylinder may be placedover the inner conductor, and the inner conductor which passes throughthe dielectric cylinder may be considered the first electrode of theprobe tip. The second electrode may preferably be a metal cylinder, e.g.a thin wall metal tube, preferably copper, which is electricallyconnected to the outer conductor of the layer-structured coaxial cable,for example by sliding over the dielectric cylinder and a portion of theouter conductor. The probe tip may have a dielectric wall thickness of0.325 mm, an outer diameter of 2.5 mm and a channel diameter of 1 mm.

The dielectric cylinder and second electrode may be set up to be of alength equal to a quarter wavelength at the frequency of operation (e.g.2.45 GHz). The dielectric material may also be chosen to provide a goodimpedance match with the low impedance environment created by theplasma. Preferably, the probe tip has a maximum length of 12 mm toenable easy access to the instrument channel. Even more preferably, thedielectric material has a dielectric constant of 5 or more.

The elongate probe may alternatively be configured to have a reducedchannel diameter through the probe tip to increase impedance of theprobe tip and allow a dielectric material with a lower dielectricconstant to be used. In some embodiments, the first electrode may be afirst conductive cylinder, such as a thin wall metal tube, preferablycopper, which is inserted at least partially into the innermostinsulating layer of the coaxial cable. The first electrode may beconnected to the inner conductive layer of the coaxial cable. Adielectric cylinder may be positioned over the first electrode.Preferably, the second electrode comprises a second conductive cylinder,e.g. a thin wall metal tube, preferably copper, which is coaxial withthe first electrode and dielectric cylinder, and which is electricallyconnected to the outer conductor of the layer-structured coaxial cable.The probe tip may have an outer diameter of 2.5 mm, a channel diameterof 0.8 mm and a dielectric wall thickness of 0.65 mm.

Preferably, the inner conductor of the layer-structured coaxial cable isa tight fit into the dielectric cylinder. In some embodiments, thedielectric cylinder may have a number of holes in the cylinder walls tomake it easier to strike the plasma. The closer the first and secondelectrodes of the probe tip are, the easier it is to strike thegenerated plasma, as this is a function of the breakdown of the gas andthe electric field produced between the electrodes—assuming that thevoltage is fixed at a peak Vmax (determined by the generator), the onlyway to increase the electric field is to reduce the distance between theelectrodes.

In one embodiment, the probe tip may have a coaxial structure that has aplasma generating region with a diameter of between 3 mm and 5 mm; i.e.the inner diameter of the second electrode within the coaxial structuremay have a diameter of between 3 mm and 5 mm, and a quartz tube thatfits tightly inside may have a wall thickness of between 0.25 mm and 1mm, and where the outer diameter of the first electrode may be between0.75 mm and 4 mm (allowing a space for gas to flow in the region betweenthe inner conductor and the inner wall of the quartz tube), anon-thermal plasma suitable for disinfection or sterilization may beproduced by operating the generator in pulsed mode with a duty cycle ofless than 40%, i.e. 28%. In one embodiment, the rms power in a singlemicrowave pulse is 50 W and the pulse ON time is 40 ms, within a totalperiod of 140 ms, i.e. the average power delivered into the plasma is14.28 W at 2.45 GHz. When an RF strike pulse is used in thisconfiguration, the duration of the RF strike pulse is around 1 ms, andthe frequency of the sinusoidal oscillations is 100 kHz. The amplitudeis around 1 kV peak (707 V_(rms)). The RF power is less than 10% of themicrowave power. The RF pulse may be synchronized to the microwave burstor pulse and triggered on the rising edge of the microwave burst orpulse.

To produce thermal plasma, the duty cycle may be increased, i.e. to 50%or continuous wave (CW) and/or the rms power level may be increased,i.e. to 75 W or 100 W for this particular probe tip geometry (if thegeometry is decreased or increased then the microwave power and theamplitude of the RF strike pulse would be adjusted accordingly). Theratio of RF to microwave power will preferably remain constant, i.e.less than 10% for non-thermal and thermal plasma.

In some embodiments, the outer electrode of the coaxial cable may beconnected to the second electrode by a conductive mesh that permits gasto flow through it. The conductive mesh may therefore be mounted in thegas conduit of the instrument, which in some embodiments may be thespace between the coaxial cable and the sleeve. In such embodiments, thespace between the coaxial cable and the sleeve may alternatively bedivided into a plurality of sub-conduits, e.g. by divider elementsconnected to or part of the sleeve. In this situation, the dividerelements or a separate connector element may provide an electricalconnection between the outer conductor of the coaxial cable and thesecond electrode. The connection may also be made by one flexible wireor strip, which may be soldered or crimped to the second electrode.

In some embodiments, where the sterilization instrument is configuredfor use as an electrosurgical instrument, the gas conduit may beconfigured to convey liquid through the elongate probe to the probe tip.This is useful in surgical procedures where fluid (e.g. saline) may beused to plump up biological tissue or flush the treatment region, e.g.to remove waste products or removed tissue to provide better visibilitywhen treating; particularly in endoscopic procedures. The proximal endof the gas conduit may terminate with a connector that allows it to beattached to a syringe used to store and introduce liquid into theconduit. Where the gas conduit is provided as a lumen through theelongate probe, the lumen or channel may comprise multiple lumina suchthat the coaxial cable may convey gas to the probe tip, or both gas andliquid to the probe tip through the plurality of lumina.

The probe tip may have any one of the structures described herein, suchas:

-   -   A unitary body (i.e. a single piece of metallized dielectric        material, e.g. ceramic or the like) suitable for use in open        surgery and key-hole (laparascopic) surgery as well as        instrument channel sterilization; and    -   A parallel plate structure (i.e. a planar transmission line        element) having a body of substantially planar dielectric        material, the first electrode being a first conductive layer on        a first surface of the planar element, and the second electrode        being a second conductive layer on a second surface of the        planar element that is opposite to the first surface.

The unitary body may have a shape that conforms to a treatment targetarea or to perform a desired function. For example, the probe tip may becurved to follow the wall of the bowel, or may be hooked to facilitatetissue removal in use as an electrosurgical instrument.

Where the parallel plate structure is used, the gas conduit may bearranged to introduce gas between the first and second conductive layers(which may be formed a two independent plates) to create non-thermal orthermal plasma that can be used to provide the return path for the RFcurrent in sterilization, or in electrosurgery. The planar transmissionline element may contain a both a region of dielectric material with ahigh dielectric constant to provide the local return path and a secondopen region that can be filled with gas to enable non-thermal plasma tobe produced for sterilization or for thermal plasma to be produced fortissue cutting or surface coagulation to be performed in electrosurgery.This arrangement may also take advantage of the use of a material with ahigh relative permittivity (or dielectric constant) inserted between thetwo conductive layers or plates (active and return conductors) . Thehigh permittivity material increases the capacitance of the structure,which in turn reduces the impedance of the structure in a linear manner,thus helping to ensure that the preferential return path for the RFcurrent is set up or exists between the two plates. When the plasma isremoved, the structure looks like a parallel plate transmission linewith air separating the two plates. This arrangement may be used toefficiently radiate microwave energy along one or more of the edges ofthe structure and/or through a single or plurality of slots or aperturescontained within one or more of the surfaces. The parallel platestructure without plasma may also be used to set-up the conditionsnecessary for RF sterilization or electrosurgery (e.g. cutting andmicrowave coagulation), i.e. at RF the structure can be modelled as aparallel plate capacitor with a dielectric material sandwiched betweenthe two plates with layers of metallization coming to the edges alongthe length of the blade and cut back at the ends and at microwavefrequency, the structure may be modelled as a distributed elementtransmission line structure capable of radiating microwave energy fromone or both long edges and/or from the distal end.

The parallel plate structure with a layer of metallization on both sidesof the dielectric material may be used to efficiently perform RFsterilization or tissue cutting in a most efficient manner when therespective layer of metallization comes right to the edge of thedielectric material, i.e. no dielectric material is exposed on thesurfaces and only metal can be seen. The dielectric can also be exposedsuch that microwave sterilization, ablation or coagulation can beperformed along the edges or at the end of the structure. It may bepreferable to remove a small amount of metallization at the distal endof the structure, i.e. 0.5 mm to 1 mm from the end, in order to preventthe device from cutting into tissue at the end if that is undesirable.

In one embodiment, the parallel plate structure may be configured asfollows:

(i) a first dielectric material comprising a block having a width of 1.5mm to 2 mm, length of 6 mm to 12 mm;

(ii) the first and second electrodes comprise layers of metallization onthe opposite surfaces of the first dielectric material that extends tothe edges on both sides of the dielectric along the length of the blade,the overall thickness of the block with layers of metallization being0.3mm to 0.5mm;

(iii) a 0.5 mm gap in the metallization forming the first electrode atthe proximal end of the first dielectric material for matching and toprevent the active conductor being shorted out;

(iv) a 0.2 mm to 1 mm gap in the metallization forming the first andsecond electrodes at the distal end of the first dielectric material toprevent the structure from cutting tissue; and

(v) a small radius of approximately 0.2 mm on the corners of the distalend of the first dielectric material to prevent the structure fromgetting stuck inside the instrument channel due to the sharp edgessnagging on the inner walls.

Where the sterilization instrument is used to emit thermal ornon-thermal plasma, a slot or plurality of slots may be provided toallow the hot gas to escape from the structure to create the effect.Non-thermal plasma may be radiated from said slots in order to enablethe same device to be used to sterilize tissue or kill bacteria withinor on the surface located in the vicinity of the probe tip, i.e. withinthe instrument channel.

The probe tip may comprise a plurality of planar transmission lineelements arranged in parallel, the plurality of planar transmission lineelements received the RF signal and the microwave signal from thecoaxial cable via a balanced power splitter arrangement. The balancedpower splitter may ensure that the RF and microwave signals are receivedby plurality of transmission line elements in phase, so that the totalemitted energy is uniform.

The probe tip may include a quarter wavelength transformer (i.e. aconnector having an electrical length equal to an odd multiple of aquarter of the wavelength at the frequency of operation) connectedbetween the coaxial cable and the plurality of planar transmission lineelements to impedance match the coaxial cable to the plurality of planartransmission line elements.

Preferably the probe tip extends beyond the coaxial cable by 8 mm orless, optimally by 5 mm or less, and may have a width of 1.8 mm or less,optimally 1.5 mm or less, and a thickness of 0.5 mm or less, optimallyabout 0.3 mm.

The first and second electrodes may form a bipolar emitting structure.The bipolar emitting structure may include a balun in the probe tip toprevent sheath currents and ensure that the microwave frequency EM fieldis radiated in an outwardly direction. The balun may be a simple thirdelectrode electrically connected (e.g. soldered) to the second electrodeat the distal end to form a short circuit. By making the balun aquarter-wavelength long (at the microwave frequency of operation), theshort circuit condition will be transformed to an open circuit conditionto prevent the flow of current along the coaxial cable. A plurality ofbaluns may be provided in the probe tip to increase the return loss whenthe probe tip is inserted into tissue. For example, one balun mayincrease the return loss from 15 dB to 25 dB, two baluns may take it to40 dB and three baluns may increase it to 60 dB, i.e. one millionth ofthe energy emanating from the probe tip is being reflected back alongthe coaxial cable.

In some embodiments, the sterilization instrument may also be configuredas an electrosurgical resection instrument for applying to biologicaltissue radiofrequency (RF) electromagnetic (EM) energy having a firstfrequency and microwave EM energy having a second frequency higher thanthe first frequency, the probe tip of the sterilization instrumentcomprising a planar body made of a first dielectric material having afirst electrode layer on a first surface and a second electrode layer ona second surface opposite the first surface wherein the inner conductorof the coaxial cable is electrically connected to the first electrodelayer and the outer conductor of the coaxial is electrically connectedto the second electrode layer to enable the probe tip to receive the RFsignal and the microwave signal, wherein the first and second electrodelayers are arranged to act as active and return electrodes to convey RFEM radiation corresponding to the RF signal by conduction, and as anantenna to radiate microwave EM radiation corresponding to the receivedmicrowave signal, and wherein first and second electrode layers may beset back from the edges of the planar body except at an RF cuttingportion located along an edge of the planar body where it is desirableto perform tissue cutting.

The probe tip may be curved in a direction between the side edges of theplanar body. For example, it may have a spoon-like shape. It may becurved (or convex) at the bottom face and be curved upwards from theproximal to distal end of the structure.

In some embodiments, the gas conduit may terminate in a rigid tube orneedle, e.g. a hypodermic needle, which may have a smaller diameter thanthe remainder of the gas conduit. The rigid tube or needle preferablyincludes a penetrating distal portion suitable for piercing biologicaltissue. This may allow fluid (saline or the like) to be injected toplump up biological tissue, for example where the instrument is used totreat the wall of the bowel. Plumping up the tissue in this manner mayhelp to reduce the risk of bowel perforation. The same rigid tube orneedle may also be used to provide gas to the probe tip, either forsurgical procedures or for sterilization of the instrument channel. Inone embodiment, the rigid tube or needle may be movable longitudinallyrelative to the probe tip, e.g. to protrude from or retract into theprobe tip.

In one embodiment, Ar gas may be introduced to the probe tip through therigid tube or needle, and a non-thermal plasma created around the edgeof the probe tip. The microwave pulse ON time may be around 40 ms, with100 ms OFF, giving a duty cycle of around 28.6%. A gated 100 kHz RFburst of around 1 kV for around 1 to 5 ms may be used, triggered by thepositive edge of the 40 ms microwave pulse. The amplitude of themicrowave power may be between 20 and 100 W, optimally around 60 W.

In some embodiments, the probe tip may be rotatable under the control ofthe sterilization instrument operator or user.

In one embodiment, rotation may be achieved by turning the coaxial cablewithin the instrument channel, e.g. using a suitable handle or controlknob. In another embodiment, the probe tip may be mounted on a rotatableplate that can turn e.g. by +/−90° relative to the instrument channel.In this arrangement, the coaxial cable may be flexible to accommodatethe movement of the probe tip during rotation. The rotatable plate maybe turned by a pair of control wires which each operate a pivoting leverengaged with the plate.

Any of the arrangements discussed in relation to the first aspect of theinvention may preferably be used with any other conventional instrumentchannel cleaning methods, such as scope washing machines or sterilizers.In particular, the probe tip may further comprise a cleaning brush whichmay be useful in removing surgical residue from the walls of theinstrument channel, particularly where such residue is not removed by EMenergy and/or thermal or non-thermal plasma.

Preferably the predetermined rate of withdrawal of the sterilizationinstrument from the instrument channel is less than 10 mm per second.For example, the predetermined rate may be less than 5 mm per second,less than 2 mm per second or around 1 mm per second. Such a rate ofwithdrawal of the sterilization instrument from the instrument channelensures that reduction in bioburden within the instrument channel isoptimised.

The sterilization apparatus described herein may preferably be used inconjunction with additional apparatus which is configured to alsosterilize the external surfaces of a scoping device. For example, theadditional apparatus may comprise a treatment chamber into which thescoping device can be loaded. Preferably, the treatment chamber isconfigured to subject the external surfaces of the scoping device to athermal or non-thermal plasma for sterilization. Even more preferably,sterilization of the external surfaces may take place while thesterilization apparatus described herein is effecting sterilization ofthe instrument channel of the scoping device.

The sterilization apparatus may thus comprise a container defining asterilization enclosure for the surgical scoping device, and a plasmagenerating unit for creating a non-thermal plasma or a thermal plasmawithin the sterilization enclosure for sterilizing an exterior surfaceof the surgical scoping device. The container may include separatechambers for different portions of the scoping device. For example, afirst chamber may receive a control head of the surgical scoping device,and a second chamber may receive an instrument tube of the scopingdevice. The plasma generating unit may include an annular body forenclosing an instrument tube of the surgical scoping device. The annularbody may be slidable along the instrument tube. For example, theadditional apparatus may comprise a conveyor or linear treatment bedwhich is configured to pass the scoping device through a staticsterilization apparatus which is configured to sterilize the externalsurfaces of the scoping device.

The withdrawal device may comprises a cable coupling element operablyconnected to the elongate probe at a proximal end thereof, and a motorarranged to drive the cable coupling element to cause relative movementbetween the elongate probe and the instrument channel in a longitudinaldirection. The withdrawal device thus allows the elongate probe (or anyinstrument cable) to be inserted or withdrawn through an instrumentchannel at a predetermined rate, the predetermined rate being set by thespeed of the motor. Preferably the motor is a variable speed motor suchthat the predetermined rate may be adjusted by a user. When used incombination with sterilization apparatus, such as described aboveaccording to the first aspect of the invention, it allows forsterilization of the instrument channel in a controlled fashion. Themotor may be powered by a battery contained within the housing, or mayalternatively be powered by an external power source, such as agenerator used to provide energy to the distal end of the instrumentcable.

The cable coupling element may be mountable in a fixed position relativeto the surgical scoping device. For example, the withdrawal device maycomprise a housing having an attachment portion for releasably attachingthe device to a handle of the scoping device. This allows theinsertion/withdrawal device and scoping device to be set up in a mannerwhich requires minimal user interaction, for example during aninstrument channel sterilization process.

The cable coupling element may comprise a plurality of rollers defininga space between them for receiving the elongate probe, the rollers beingarranged to grip an exterior surface of the elongate probe wherebyrotation of the rollers causes longitudinal movement of the elongateprobe.

In certain embodiments, the motor is switchable between a forward modeand a reverse mode of operation, wherein the forward mode is suitablefor inserting the instrument cable through the instrument channel andthe reverse mode is suitable for withdrawing the instrument cablethrough the instrument channel. This allows the same device to be usedmultiple times for different purposes, though it is also envisaged thatthe device be disposable to ensure sterile equipment is used whereneeded. Providing a device which can run in both forward and reversemodes reduces costs and complications for a user, as they can simplychoose which mode the device is operated in rather than buying separateinsertion and withdrawal devices. Production costs are also reduced asonly a single unit need be produced, suitable for each purpose.

Preferably, the device may further comprise a drum around which theinstrument cable may be wound prior to insertion or during withdrawal ofthe instrument cable through the instrument channel. This simplifies theinsertion or withdrawal procedure as the user does not need to worryabout storing the instrument cable before or after use, or feeding thecable into or out of the scoping device. By winding the instrument cableabout a drum, storage space and working space (e.g. during asterilization process) may be minimized. Preferably, the drum is alsocontained in the housing so that the drum may provide a sterileenvironment for storage of the instrument cable. The drum may preferablybe sized such that the bending radius of the instrument cable about thedrum is sufficient to prevent damage to the cable, particularly wherethe instrument cable is likely to be re-used.

Preferably, the device further comprises means for disengaging the motorfrom the at least one roller to allow a user to freely slide the devicealong the instrument cable. In this way, the device can easily be slidonto or removed from the instrument cable and a user can properlyposition the device on the instrument cable. Disengaging the motor alsoallows a user to manually slide the instrument cable in an instrumentchannel if necessary, for example, during a sterilization process. Thismay be useful, for example, if there is a blockage or unexpected problemwith the equipment.

Preferably, the plurality of rollers are biased towards each other. Insome embodiments, the rollers may have an hourglass shape. Thesefeatures ensure that there is a good fit between the rollers and thesurface of the instrument cable, increasing friction to ensure that theinstrument cable is smoothly pulled by the rollers and that there is noslipping of the rollers. This increases reliability of the device aswell as ensuring that the speed of cable insertion/withdrawal isconsistent with the speed selected or desired by the user.

In some embodiments, the motor may be a stepper motor. This may beparticularly advantageous if the device is used with sterilizationapparatus, as a stepper motor can be used to ensure that the instrumentchannel is properly sterilised at each step by waiting for apredetermined amount of time before withdrawing the instrument cable afurther distance increment.

Preferably, each of the plurality of rollers is made from a plastic orsilicone material. Such materials may be chosen to give a highcoefficient of friction between the surface of the rollers and of theinstrument cable, ensuring a complete transfer of motion from therollers to the instrument cable. In addition, the use of a plastic orsilicone material ensures that no damage is done to the instrument cableby the rollers.

The withdrawal device may be an independent aspect of the presentdisclosure. According to that aspect, there is provided a probewithdrawal device for moving an elongate probe through an instrumentchannel of a surgical scoping device, the probe withdrawal devicecomprising: a cable coupling element operably connected to the elongateprobe at a proximal end thereof; and a motor arranged to drive the cablecoupling element to cause relative movement at a predetermined ratebetween the elongate probe and the instrument channel in a longitudinaldirection.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of examplewith reference to the accompanying drawings in which:

FIGS. 1A and 1B show a sterilization apparatus according to a firstaspect of the invention;

FIG. 2 shows sterilization apparatus and an alternative embodiment of awithdrawal device;

FIG. 3A is a cross-sectional view through a distal end of the elongateprobe showing the probe tip and coaxial cable; FIG. 3B shows the probetip of FIG. 3A alone;

FIG. 3C shows the coaxial cable of FIG. 3A alone;

FIG. 4 is a cross-sectional view through an alternative probe tipembodiment;

FIG. 5 is a cross-sectional view through another alternative probe tiparrangement;

FIG. 6 is a cross-sectional view through yet another embodiment of aprobe tip;

FIG. 7 is a longitudinal cross-sectional view through a coaxial plasmaapplicator (probe tip) that can be used with the present invention;

FIG. 8 is a longitudinal cross-sectional view through a waveguide plasmaapplicator (probe tip) that can be used with the present invention;

FIG. 9 is a longitudinal cross-sectional view through an integratedmicrowave cable assembly and plasma applicator probe tip that can beused with the present invention;

FIG. 10 is a longitudinal cross-sectional view through another coaxialplasma applicator (probe tip) that can be used with the presentinvention;

FIG. 11 is a longitudinal cross-sectional view through another coaxialplasma applicator (probe tip) that can be used with the presentinvention;

FIG. 12 is a longitudinal cross-sectional view through another elongateinstrument 290 that can be used with the present invention;

FIG. 13 is a longitudinal cross-sectional view through another probe tipthat can be used with the present invention;

FIG. 14 is a longitudinal cross-sectional view through a withdrawaldevice that can be used with the present invention;

FIG. 15 is a lateral cross-sectional view through driving components inthe withdrawal device of FIG. 14;

FIG. 16 is a longitudinal cross-sectional view through anotherwithdrawal device that can be used with the present invention;

FIGS. 17A to 17C show a sterilization apparatus in use for sterilizingthe instrument channel of a scoping device;

FIG. 18 is a schematic view of a probe tip which may be used with thepresent invention; and

FIG. 19 is an end view of the probe tip of FIG. 18.

DETAILED DESCRIPTION; FURTHER OPTIONS AND PREFERENCES

FIG. 1A shows a sterilization apparatus 10 according to a first aspectof the invention. The sterilization apparatus comprises an elongateprobe having a coaxial cable 12 and a probe tip 14 at its distal end. Agenerator 30 is connected to the coaxial cable at its proximal end. Agas supply 40 is also connected to supply gas to the probe tip 14through a gas conduit (not shown) in the coaxial cable 12. A withdrawaldevice 20 is positioned on the coaxial cable 12 in order to withdraw theelongate probe from an instrument channel which runs through theinsertion tube 52 of scoping device 50, in a manner which will beexplained in more detail below.

FIG. 1B shows the sterilization apparatus 10 in use. The elongate probeis within the instrument channel of the insertion tube 52, and thewithdrawal device 20 is attached to the handle of the scoping device 50.The withdrawal device 20 is switched on to withdraw the coaxial cable 12from the instrument channel of the insertion tube 52 at a predeterminedrate, in a direction indicated by arrow 18. While the withdrawal device20 is withdrawing the coaxial cable 12 and probe tip (not shown) throughthe instrument channel, the generator 30 is supplying RF and/ormicrowave frequency EM energy to the probe tip such that the probe tipis sterilizing the instrument channel. The gas supply 40 supplies gas tothe probe tip through the gas conduit so that the RF and/or microwave EMenergy may be used to generate a non-thermal plasma at the probe tip todestroy or eliminate micro-organisms in the instrument channel of theinsertion tube 52.

FIG. 2 shows sterilization apparatus having an alternative withdrawaldevice 20. In this arrangement, the withdrawal device additionallycomprises a drum 22 around which the coaxial cable 12 is wrapped as itis withdrawn from the instrument channel of the scoping device 50. Thegenerator 30 supplies RF and/or microwave EM energy to the coaxial cable12 via a connecting wire 32 and a suitable plug on the housing of thewithdrawal device 20. Similarly, gas from the gas supply 40 is conveyedto the gas conduit through a connecting tube 42. The withdrawal device20 is discussed in more detail below.

FIG. 3A is a cross-sectional view through a distal end of the elongateprobe showing the probe tip 14 and a layer-structured coaxial cable 12,with a catheter 110 and probe tip 14 inserted in a channel 130 of thecoaxial cable 12.

The probe tip 14, which is shown alone in FIG. 3B, used in sterilizationof an instrument channel but may also be suitable for use inelectrosurgery. In particular, the probe tip 14 shown in FIGS. 3A and 3Bis configured for use as a resection instrument.

The probe tip 14 comprises a connection collar 152 attached to thedistal end of the catheter 110, an extension sleeve 154 which extendsdistally from the connection collar 152, and a sterilization instrumentconnected at a distal end of the extension sleeve 154. The sterilizationinstrument is formed from a piece of rigid dielectric 144 that has aconductive coating (not shown) on its upper surface 146 and lowersurface 148 to form two electrodes, and a smooth tapering dielectric 150formed below the lower surface 148. The connection collar 152 comprisesa short rigid cylindrical portion having a diameter selected to snuglyfit in the channel 130 of the coaxial cable so that its outer surface isin physical contact with the surface that defines the channel 130 (i.e.the inner surface of wall 134). The connection collar 152 may have alarger diameter than the catheter 110. A pair of contacts 156, 158 areformed on the outer surface of the connection collar 152. The contacts156, 158 may extend around all or part of the outer surface. In thisembodiment, a back (i.e. proximal) contact 156 is arranged toelectrically connect to the inner conductive layer 140 of thelayer-structured coaxial cable 12, and a forward (i.e. distal) annularcontact 158 is arranged to electrically connect to the outer conductivelayer 136 of the layer-structured coaxial cable 12.

To achieve these electrical connections, the coaxial cable 12 has a pairof longitudinally spaced terminals 160, 162 that protrude through theinnermost layer 142 at the distal end of the channel 130, as shown inFIG. 3C. The terminals 160, 162 may extend around all or part of theinner surface of the channel 130. In this embodiment, a back (i.e.proximal) terminal 160 extends through the innermost layer 142 from adistal end of the inner conductive layer 140, and a forward (i.e.distal) terminal 162 extends through both the dielectric layer 138 andthe innermost layer 142 from a distal end of the outer conductive layer136. The outer conductive layer 136 extends longitudinally beyond adistal end of the inner conductive layer 140. The inner conductive layer140 thus terminates at the back terminal 160, i.e. there is a gap 164(e.g. an air gap or other insulating material) located beyond of thedistal end of the inner conductive layer 140 before the forward terminal162.

A conductive rod 166 extends from the back contact 156 through theextension sleeve 154 to provide an electrical connection for theconductive coating on the upper surface 146 of the piece of rigiddielectric 144. The upper surface 146 is therefore electricallyconnected to the inner conductive layer 140 of the coaxial cable 14.Similarly, a conductive rod 168 extends from the forward contact 158through the extension sleeve 154 to provide an electrical connection forthe conductive coating on the lower surface 148 of the piece of rigiddielectric 144. The lower surface 148 is therefore electricallyconnected to the outer conductive layer 136 of coaxial cable 12.

The extension sleeve 154 may be a rigid tube of dielectric material forboth protecting and electrically insulating the conductive rods 166,168. The extension sleeve 154 may have an electric length thatcorresponds to half a wavelength of the microwave energy that isconveyed by the extension sleeve 154. The conductive rods 166, 168 maybe separately enclosed (e.g. coated of otherwise covered) by dielectric,e.g. glue, plastic or some other insulator, to prevent breakdown,especially where they are close together.

A distal end of the connection collar 152 may abut against a stop flange170 formed at the distal end of the channel 130. The probe tip 14 cantherefore be secured in place with an electrical connection between thecontacts 156, 158 and terminals 160, 162, e.g. by maintaining a pushingforce on the catheter 110. Although in this embodiment the connectioncollar 152 performs a dual function of electrical connection andphysical stop, it is possible for these functions to be performed byseparate features, in which case the connection collar 152 may belocated further back in the channel 130 and the extension sleeve 154 maybe longer.

To prevent material escaping backwards into the channel, a seal 172 maybe formed over the entrance to the channel 130.

The catheter 110 may be a hollow tube for conveying a gas conduit orcontrol lines 178 to the probe tip 14. In this embodiment, the gasconduit extends right through to the distal end of the probe tip fordelivering argon or another gas for plasma sterilization. The gasconduit 178 may also be adapted to deliver fluid such as saline to theprobe tip 14 for performing electrosurgery.

FIG. 4 shows another embodiment of a probe tip 14 which can be used withthe layer-structured coaxial cable 12 described above with respect toFIGS. 3A-3C. The probe tip 14 comprises an extension of the innermostlayer 142 and inner conductive layer 140. In this embodiment, theinnermost layer 142 is a PTFE tube. The inner conductive layer acts as afirst electrode of the probe tip 14. The probe tip 14 also comprises adielectric material 182 which is placed over the first electrode 140,and a second electrode 180 over the dielectric material 182. Thedielectric 182 is a MACOR cylinder and the second electrode 180 isformed of a thin wall copper tube. The second electrode 180 iselectrically connected to the outer conductive layer 136, which extendsbeyond the distal end of a sleeve 184 covering the coaxial cable 12. Gasmay be supplied to the distal end of the probe tip 14 through thechannel 130, which extends through the elongate instrument to itsproximal end where gas may be supplied e.g. from a gas canister. Theprobe tip 14 has an outer diameter of 2.5 mm, the dielectric layer 182has a wall thickness of 0.325 mm, and the channel 130 a diameter of 1mm.

FIG. 5 shows an alternative probe tip 14 which can be used with thelayer-structured coaxial cable 12 described above with respect to FIGS.3A-3C. The probe tip 14 comprises a first electrode 186 which is a tubestructure inserted into the innermost layer 142, and which defines partof the channel 130. The innermost layer 142 may be a PTFE tube.Dielectric layer 182 is provided over the first electrode 186. Similarto the embodiment shown in FIG. 4, the second conductor 180 is a thinwall copper cylinder connected to the outer conductive layer 136. Thefirst electrode 186 is connected to the inner conductive layer 140 via ametal ring 188 which is gripped between the dielectric material 182 andthe innermost layer 142. The outer diameter of the probe tip 14 is 2.5mm, the channel 130 has a diameter of 0.8 mm and the dielectric 182 hasa wall thickness of 0.65 mm. The reduced channel 130 diameter andincreased dielectric 182 thickness increases the impedance of the probetip 14, allowing a lower dielectric constant material to be used for thedielectric layer 182.

Other probe tip embodiments discussed herein may also be used with a‘conventional’ coaxial cable; i.e. a coaxial cable not having thelayered structure described above.

FIG. 6 shows a cross-sectional view through a probe tip which issuitable for generating plasma at the distal end of an elongateinstrument. The tip shown may also be used as an electrosurgicalinstrument. The elongate instrument 500 is cylindrical, and sized to fitdown the instrument channel of a scoping device, e.g. an endoscope. Theinstrument comprises a coaxial cable 502 having an inner conductor 504and an outer conductor 506 separated from the inner conductor 504 by adielectric material 508. The outer conductor 506 is exposed around atthe outside surface of the coaxial cable 502. At the distal end of thecoaxial cable 502, the inner conductor 504 extends beyond the outerconductor 506 and is surrounding by a dielectric cap 510, e.g. made ofPEEK or the like. The cap 510 is a cylinder having substantially thesame diameter as the coaxial cable 502. The distal end of the cap 510forms a rounded, e.g. hemispherical dome. The inner conductor 504terminates at its distal end at a rounded tip 512 which projects beyondthe end of the cap 510. The coaxial cable 502 is mounted within a sleeve514, which preferably includes internal braids (not shown) to impartstrength. The sleeve is dimensioned to fit within the instrument channelof a scoping device. There is an annular gap 516 between the innersurface of the sleeve 514 and the outer surface of the coaxial cable 502(i.e. the exposed outer conductor) which forms a gas conduit forconveying gas introduced at the proximal end of the sleeve 514 to thedistal end. A conductive terminal tube 518 is mounted at the distal endof the sleeve 514. For example, the conductive terminal tube 518 may bewelded to the sleeve 514.

In the configuration shown in FIG. 6, the rounded tip 512 of the innerconductor 504 forms a first electrode and the conductive terminal tube518 forms a second electrode. An electric field for striking a plasma inthe gas flowing from the annular gap 516 is formed between the firstelectrode and second electrode by applying suitable energy (e.g. RFand/or microwave frequency energy) to the coaxial cable. The conductiveterminal tube 518 is electrically connected to the outer conductor 506of the coaxial cable 502 by a plurality of radially projecting bumps 520on the inner surface of the conductive terminal tube 518. There may betwo, three, four or more bumps 520 spaced from one another around theinner circumference of the conductive terminal tube 518. Spacing thebumps in this manner permits gas to flow past. An insulating liner 522is mounted around the inside surface of the conductive terminal tube 518along a distal length thereof. The insulating liner 522 may be made ofpolyimide or the like. The purpose of the liner 522 is to provide asuitable dielectric barrier between the first electrode and secondelectrode to ensure that the applied RF and/or microwave frequencyenergy results in an electric field with high voltage for striking theplasma. There is a small gap between the liner 522 and the cap 510 topermit gas to flow past.

FIG. 7 is a longitudinal cross-sectional view through a coaxial plasmaapplicator (probe tip) that can be used in the present invention. Theplasma sterilization apparatus need not be limited to use with this typeof structure. Indeed this example is provided to explain the theorybehind the use of voltage transformers (or impedance transformers) inthe generation of plasma in the applicator. In fact it may be possibleto generate the plasma without voltage transformers, especially if animpedance adjustor is present. The plasma applicator 300 shown in FIG. 7is a coaxial structure comprising three quarter wave impedancetransformers, where the diameter of the center conductor is changed toproduce three sections with different characteristic impedances. Theimpedances are chosen such that the voltage at the distal end of thestructure is much higher than the voltage at the proximal (generator)end of the structure.

If the physical length of each section is equal to an odd multiple ofthe quarter electrical wavelength, i.e.

${L = \frac{\left( {{2n} - 1} \right)\lambda}{4}},$

where L is length in meters, n is an integer, and λ is wavelength atfrequency of interest in meters, then the following equation applies

Z₀=√{square root over (Z_(L)Z_(S))},

where Z₀ is the characteristic impedance of the coaxial line in ohms,Z_(L) is the load impedance seen at the distal end of the section inohms, and Z_(S) is the source impedance seen at the proximal end of thesection in ohms. By algebraic manipulation of this equation, the loadimpedance can be expressed as

$Z_{L} = {\frac{Z_{0}^{2}}{Z_{S}}.}$

It can therefore be seen that if the characteristic impedance of thetransformer section is high and the source impedance is low then theload impedance can be transformed to a very high value. Since the powerlevel at the generator end of the antenna should theoretically be thesame as that at the load end, the following can be stated

${P_{i\; n} = {\left. P_{out}\Rightarrow P_{i\; n} \right. = \frac{V_{L}^{2}}{Z_{L}}}},$

which means the voltage at the distal end can be expressed asV_(L)=√{square root over (P_(in)Z_(L))}. Thus it can be seen that ifZ_(L) can be made as large as possible then the value of the voltage atthe distal end of the antenna structure V_(L) will also be very large,which implies that the electric field will also be high. Since it isrequired to set up a high electric field in order to strike the plasma,it may be seen that this structure can be used to set-up the correctconditions to strike the plasma.

Considering the structure shown in FIG. 7, the microwave generator 3000is indicated schematically as having a source impedance (Z_(S)) 308. Thepower from the generator 3000 enters the applicator 300 via a coaxialcable (not shown) using microwave connector 340. Connector 340 may beany microwave connector that is capable of operating at the preferredfrequency of operation and can handle the power level available at theoutput of power generator 3000, e.g. N-type or SMA type connectors maybe used. Microwave connector 340 is used to launch the microwave powerinto the plasma generating region, which includes an antenna structuredescribed below. The first stage of the antenna structure is a 50 Ωcoaxial section that consists of a center inner conductor (a firstelectrode) with an outside diameter b and an outer conductor (a secondelectrode) with an inside diameter a. The space between the inner andouter conductors contained within the first section is filled with adielectric material 342, which is labelled here as PTFE. Thecharacteristic impedance of the first section of the antenna is shownhere to be the same as that of the generator, i.e. 50 Ω, and can bedescribed as follows

${Z_{0} = {Z_{S} = {{\frac{138}{\sqrt{ɛ_{r}}}\log_{10}\frac{a}{b}} = {50\mspace{14mu} \Omega}}}},$

where ε_(r) is the relative permittivity of the filler material, Z₀ isthe characteristic impedance of the first section and Z_(S) is thesource impedance (or the generator impedance). The second section is thefirst quarter wave impedance transformer 311 whose characteristicimpedance Z₀₁ is higher than that of the first section and can becalculated using

${Z_{01} = {138\; \log_{10}\frac{c}{b}}},$

where c is the inside diameter of the outer conductor 312. Since thesecond section is filled with air (or at least the gas from gas feed470), the relative permittivity ε_(r) is equal to unity and so thesquare root term disappears from the equation that describes theimpedance of a coaxial transmission line. A practical example of theimpedance of the second section may be b=1.63 mm and c=13.4 mm. Withsuch dimensions, Z₀₁ would be 126.258 Ω.

The third section is the second quarter wave impedance transformer 310,whose characteristic impedance Z₀₂ is lower than that of the firstsection and second sections, and can be calculated using

${Z_{02} = {138\; \log_{10}\frac{c}{d}}},$

where d is the outer diameter of the inner conductor. It is desirable totaper the input and output ends of the center conductor in order to makethe step from the high impedance condition to the low impedancecondition more gradual in order to minimize mismatches occurring at thejunctions between the two impedances. A suitable angle for the taper is45°. A practical example of the impedance for the third section may bed=7.89 mm and c=13.4 mm. With such dimensions, Z₀₂ would be 31.744 Ω.

The fourth section is the final section and consists of a third quarterwave impedance transformer 320, whose characteristic impedance Z₀₃ ishigher than that of the third section, and can be calculated using

${Z_{03} = {138\; \log_{10}\frac{c}{e}}},$

where e is the outer diameter of the inner conductor. It is desirablefor the distal end of the inner conductor to be sharp and pointed inorder to maximize the magnitude of the electric field produced at thispoint. A practical example of the characteristic impedance for thefourth section may be e=1.06 mm and c=13.4 mm. With such dimensions, Z₀₃would be 152.048 Ω.

For the arrangement using three quarter wave transformers as shown inFIG. 7, the load impedance Z_(L) seen at the distal end of the antennamay be expressed as

$Z_{L} = {\frac{Z_{03}^{2}Z_{01}^{2}}{Z_{02}^{2}Z_{S}}.}$

Using the values of characteristic impedance calculated above for thethree transformers, Z_(L) would be 7,314.5 Ω. If the input power is 300W, then the voltage at the output will be V_(L)=√{square root over(P_(in)Z_(L))}=1481.33V. The electric field generated at the end of thisstructure will thus be

$E = {\frac{2V_{L}}{c} = {221094.03\; {{Vm}^{- 1}.}}}$

This large electric field may enable the plasma to be set up using anyone of a number of gases and gas mixtures.

The inner conductor may be a single conductor whose diameter changesfrom b to d to e from the proximal end to the distal end. The outerconductor has the same inner diameter c for the length of the threeimpedance transformer sections and is reduced to a at the first section.The material used for the inner and outer conductors may be any materialor composite that has a high value of conductivity, for example, copper,brass, aluminum, or silver coated stainless steel may be used.

The gas or mixture of gases is fed into the structure via gas conduit470 and the gas fills the interior (the plasma generating region) of theplasma applicator. The applicator is dimensioned to fit within theinstrument channel of a scoping device.

FIG. 8 shows a plasma applicator probe tip 300 in which a waveguidecavity is used to create the field to generate the plasma. In thisparticular embodiment, an H-field loop 302 is used to transfer themicrowave energy from the microwave generator into the waveguideantenna, and the gas mixture is introduced into the structure via gasfeed 471, which is connected to gas conduit 470. It may be preferablefor H-field loop to have a physical length that is equal to half thewavelength at the frequency of interest or operation, and for the distalend of said loop to be connected to the inside wall of outer conductor.The connection may be made using a weld or solder joint. The H-fieldloop may be considered a first electrode and the waveguide antenna asecond electrode.

Although not illustrated in FIG. 8, impedance transformers may also beintroduced into the waveguide embodiment to generate high electricfields at the distal end of the applicator. In other words, thewaveguide antenna may comprise of a plurality of sections that have alength equal to an odd multiple of the quarter loaded or unloadedwavelength at the frequency of interest, i.e.

$L = {\frac{\left( {{2n} - 1} \right)\lambda}{4}.}$

In order to reduce the dimensions of the waveguide (length, width, ordiameter) the waveguide may be filled with a dielectric, or magnetic, orcomposite material where the wavelength is reduced by a function of theinverse of the square root of the relative permittivity, or the relativepermittivity, or the product of the two. A number of impedancetransformers may be introduced by loading one or a plurality of thesections that form the transformer. In the instance whereby thewaveguide structure is loaded with a dielectric or magnetic material (orcombination of the two), it may be preferable for the loading materialto be porous or have a plurality of holes drilled into it to enable thegas or gas mixture to flow inside the waveguide sections.

In order to change the impedance of the waveguide to produce the desiredquarter wavelength transformations within the structure, it is necessaryto make adjustments to the geometry of the structure or change theloading material. For a rectangular waveguide, the characteristicimpedance of the waveguide cavity may be expressed as

${Z_{0} = {377\frac{b}{a}\sqrt{\frac{\mu_{r}}{ɛ_{r}}\frac{\lambda_{g}}{\lambda}}}},$

where

$\frac{\lambda_{g}}{\lambda}$

is

$\frac{1}{\sqrt{1 - f_{{c/2}f}}},$

b is the height of the guide (or the length of the short wall), a is thewidth of the guide (or the length of the long wall), μ, is the relativepermeability of the magnetic loading material, ε, is the relativepermittivity of the dielectric loading material, f_(c) is the cut offfrequency of the guide, and f is the frequency of operation.

In FIG. 8, an additional material 360 is added at the distal end of thewaveguide. The additional material 360 may be a quartz tube used toincrease the electric field at the distal end of the antenna structure.

FIG. 9 provides a detailed diagram of a probe tip comprising anintegrated microwave cable assembly and plasma applicator. In thisarrangement, the integrated gas and microwave cable assembly comprises acoaxial arrangement formed using two tubes. The first tube 314 is arelatively thick walled tube made from a flexible dielectric materialand is coated with a layer of metal (e.g. a metallization layer of highconductivity, e.g. made from silver, copper or gold) on both the innerand outer walls 318, 319 thereof. The second tube 313 is a relativelythin walled tube made from a flexible material. The first tube 314 issuspended inside the second tube 313 using spacers 312 that may be madefrom a metallic or dielectric material and must allow gas to flow withinand along the channel formed between the outer wall 318 of first tubeand the inner wall of second tube 313. The plasma applicator comprisestwo impedance transformers 310, 320, a gas conduit 315 from centerchannel of first tube 314 into the applicator, and a gas extractionpassage 316 from the applicator along a channel formed between the outerwall of first tube and the inner wall of second tube. A first section321 of the inner channel used to feed gas into the applicator is solidto enable the center pin within microwave connector 340 to beelectrically connected to the new microwave cable assembly. The inputmicrowave connector may be any connector suitable for carrying microwavepower up to 600 W CW at the frequency of interest, e.g. SMA or N-typeconnectors may be used. Microwave power is delivered to the connector340 from a generator.

The center 311 of the inner conductor 319 used to form the coaxialmicrowave cable assembly is hollow due to the fact that the microwavefield produced at the frequency of interest only requires a small amountof wall thickness to enable the field to efficiently propagate along thecable or waveguide, thus the center portion 311 of inner conductor 319may be transparent to the microwave field. Similar criteria apply to thethickness of the outer conductor 318, i.e. it is only a thin layer 318on the outer surface of the first tube 314 that plays an important partin the microwave field or wave propagation along the wave guidingchannel. The first tube 314 should preferably be made from a low lossdielectric material, e.g. low density PTFE, in order to ensure that thepower loss along the structure (the insertion loss) is minimized. Theintegrated applicator or antenna is formed inside second tube 313 andforms an integral part of the cable assembly, aiding insertion of thedevice through an instrument channel, e.g. of an endoscope. The plasmaapplicator shown in FIG. 9 consists of two quarter wave impedancetransformer sections 310, 320. The first section is a low impedancesection whose impedance is determined by the ratio of the diameter ofinner conductor (g) and the diameter of outer conductor (i) as describedabove. The outer conductor may be an extension of outer conductor 318within the integrated microwave cable assembly used to transport themicrowave energy from the generator to the applicator. The gas fromwithin channel 311 is fed into the applicator through a hole, groove, orchannel made in inner conductor 311. The second transformer section is ahigh impedance section whose impedance is determined by the ratio of thediameter of inner conductor (h) and the diameter of outer conductor (I).The material used to form inner conductor may be a material that is ableto withstand high temperature without change of physical form orcharacteristic, e.g. tungsten.

A quartz tube 319 is located at the distal end of the applicator betweenthe inner and outer conductors. The quartz tube reduces the likelihoodof arcing and promotes plasma striking in the plasma generating region.Here the plasma plume 1000 is directed out of the open end of theapplicator by the flow of gas from the center channel 311. An annulargap between the quartz tube and outer conductor leads to the outerchannel 316. This channel may be connected to a pump for extractingexcess or residual gas from the sterilization site.

FIGS. 10 and 11 show two elongate instrument structures 250, 252 that,in addition to performing sterilization of an instrument channel, may beused to cut, coagulate, ablate and sterilize biological tissue. Theoverall diameter of these structures may range from less than 1 mm togreater than 5 mm. In both cases, the instrument structures 250, 252comprise a coaxial cable 254 having a connector 256 at a proximal end toreceive microwave frequency energy and RF energy from a generator (notshown). The coaxial cable 254 has an inner conductor 258 separated fromand coaxial with an outer conductor 260 by a suitably low lossdielectric material 262, which may be low density PTFE, a micro-porousmaterial such as Gortex® or the like.

In this embodiment, a distal portion of the inner conductor 258 ishollowed out to form a conduit 264 extending toward the instrument tip266, 268. It is possible to make inner conductor 258 hollow by makinguse of the skin effect in conductors that occurs at microwavefrequencies.

When a conductive material is exposed to an EM field, it is subjected toa current density caused by moving charges. Good conductors, such asgold, silver and copper, are those in which the density of free chargesare negligible and the conduction current is proportional to theelectric field through the conductivity, and the displacement current isnegligible with respect to the conduction current. The propagation of anEM field inside such a conductor is governed by the diffusion equation,to which Maxwell's equations reduce in this case. Solving the diffusionequation, which is valid mainly for good conductors, where theconduction current is large with respect to the displacement current, itcan be seen that the amplitude of the fields decay exponentially insidethe material, where the decay parameter (δ) is described using thefollowing equation:

${\delta = \frac{1}{\sqrt{\frac{\omega \; \mu \; \sigma}{2}}}},$

wherein δ is known as the skin depth and is equal to the distance withinthe material at which the field is reduced to 1/e (approximately 37%) ofthe value it has at the interface, σ is the conductivity of thematerial, μ is the permeability of the material, and ω is the radianfrequency or 2nf (where f is the frequency). From this, it can be seenthat the skin depth decreases when the frequency of the microwave energyincreases as it is inversely proportional to the square root of thisfrequency. It also decreases when the conductivity increases, i.e. theskin depth is smaller in a good conductor than it is in another lessconductive material.

For the microwave frequencies of interest and the materials of interestfor implementing the structures shown in FIGS. 10 and 11, the skin depthis around 1 μm, hence the inner conductor/first electrode 258 used inthe construction of the instruments described here require a wallthicknesses of only about 5 μm to enable most of the microwave field topropagate. This implies that a hollow center conductor can be usedwithout causing any change to the EM wave propagating along thestructure.

A fluid feed inlet 270 is formed through the side of the coaxial feedcable 254 to permit an external fluid (gas and/or liquid) supply tocommunicate with the conduit 264 to deliver fluid to the probe tip 266,268. Preferably, the fluid feed does not affect the electromagneticfield that has been set up in the co-axial transmission line structure.EM modelling is performed to determine optimal feed points where the EMfield is unaffected.

FIG. 10 is a longitudinal cross-sectional view through a probe tip fordelivering plasma, wherein the probe tip has a coaxial structure. InFIG. 10, the probe tip 266 includes an outlet 272 from the conduit,which permits the gas to enter the interior of the probe tip 266 inwhich the dielectric material 262 is removed, which may form a plasmageneration region 274. In this particular arrangement, the outlet 272comprises a plurality of slots on the inner conductor/first electrode258 within the plasma generation region 274. In the plasma generationregion 274, the electric field set up by the microwave frequency EMenergy and/or RF field ionizes the gas to produce plasma in the sameregion. The plasma may be thermal or non-thermal and may be used tosterilize the instrument channel of a scoping device, sterilize tissue,provide a local return path for the RF current, produce surfacecoagulation and/or assist with tissue cutting. The plasma may be formedin the cavity by initially using energy at the RF frequency to providethe voltage necessary to strike the plasma and then using energy at themicrowave frequency to enable the plasma to be sustained. Where thedistance between the outer surface of the inner conductor and the innersurface of the outer conductor is very small, i.e. less than 1 mm, themicrowave field may be used to strike and maintain plasma. Similarly, itmay only be necessary to use the RF field to produce both non-thermalplasma for sterilization and thermal plasma for surface ablation and/ortissue cutting.

The distal end 276 of the inner conductor/first electrode 258 in theprobe tip 266 is a solid pointed section, which may take the form of asharp needle with a small diameter, i.e. 0.5 mm or less, which may beparticularly effective when performing tissue cutting. The distal end277 of the plasma generation region 274 is open to permit plasma to bedelivered out of the elongate instrument.

A quarter wave (or odd multiple thereof) balun 278, comprising a thirdcoaxial conductor that is shorted at its distal end and open at itsproximal end is connected to the structure to prevent microwave currentsfrom flowing back along the outer conductor 260 to the coaxial cable254, which can cause the profile of the microwave energy to becomenon-optimal.

The composition of gas and its flow rate and delivery profile, togetherwith the power level and profile of the supplied RF EM energy and/ormicrowave EM energy determines the type of plasma that is set up inplasma generation region 274 of the elongate instrument.

FIG. 11 is a longitudinal cross-sectional view through another coaxialplasma applicator. The elongate instrument 252 in FIG. 11 has a similarprobe tip structure to the instrument shown in FIG. 10 except that outerconductor/second electrode 260 has been continued such that it endscloser to the distal end 276 of the inner conductor/first electrode 258in the probe tip 268. Here the outer conductor 260 takes the form of apointed cone at the distal end of the probe tip 268. The slope of outerconductor/second electrode may be at the same angle as the slope of thesolid pointed section. A jet of plasma may be emitted through a smallgap 280 that separates the inner conductor 258 from the outer conductor260 in this region.

The probe tip may be arranged such that the initial ionization dischargeor breakdown of the gas occurs between the distal end of the outerconductor 260 and the solid pointed section of the inner conductor 258.The solid pointed section may be cone shaped, which is a preferredstructure for use as a surgical instrument.

FIG. 12 depicts an elongate instrument 290 suitable for use in thepresent invention. The probe tip shown is suited for gastrointestinalprocedures in addition to instrument channel sterilization. The elongateinstrument 290 comprises a coaxial cable 254 having an inner conductor258 separated from and coaxial with an outer conductor 260 by adielectric material 262. A probe tip 292 is connected at the distal endof the coaxial cable 254. A connector 256 is connected to the proximalend of the coaxial cable to receive RF EM energy and microwave frequencyEM energy from a generator.

The probe tip 292 is a unitary piece of dielectric material (e.g. lowloss Dynallox® Alumina) having two separate layers of metallizationformed thereon to form first and second electrodes. The inner conductor258 of the coaxial cable 254 extends beyond the distal end of thecoaxial cable 254 into the interior of the probe tip 292. From there itis electrically connected to one of the layers of metallization. Theouter conductor 260 of the coaxial cable 254 is connected to the otherlayer of metallization. The probe tip 292 is fixed to the coaxial cable254 by a sleeve 294 (e.g. of stainless steel), which may be crimped toforce securing tabs 296 into corresponding notches in the ceramic bodyof the probe tip 292. The length of the sleeve 294 may be selected tomatch the impedance of the probe tip 292 to the coaxial cable 254, i.e.it may act as a tuning stub.

The layers of metallization are provided on the side surfaces of theprobe tip 292. The layers are separated from each other by the ceramicso that it effectively forms a planar transmission line. In thisembodiment, the layers of metallization are set back from the side edgesand the distal edge of the probe tip except at regions where it isdesired to emit an RF EM field. FIG. 12 shows schematically a firstlayer of metallization 298 which is set back slightly from the edges ofthe probe tip except along a region along the bottom edge.

In this embodiment, the probe tip 292 has a hooked shape where one ofthe edges of the probe tip 292 curves inwards and outwards, i.e. definesa recess. The recess may include a substantially proximally facingsurface for facilitating tissue removal, e.g. by permitting tissue to bepulled, scooped or scraped away from the treatment site. The regionalong the bottom edge (the RF cutting region) to which the first layerof metallization 298 extends is on the inside of the recess.

The length of the probe tip 292 that extends from the sleeve 294 todeliver RF and microwave energy may be between 3 mm and 8 mm, preferably4 mm. The width of the probe tip may be similar to the diameter of thecoaxial cable, e.g. between 1.1 mm and 1.8 mm, preferably 1.2 mm. Thethickness of the distal part of the probe tip 292 may be between 0.2 mmand 0.5 mm, preferably 0.3 mm.

The general shape of the distal end of the instrument is of a spoon orscoop having a radius commensurate with that of the inner region of thevessel (e.g. bowel) in which treatment is to take place. For example,the curved arrangement shown may be suitable for getting underneath apolyp and scooping it out.

The instrument may incorporate a gas conduit (not shown) to provide agas supply to the probe tip for production of thermal or non-thermalplasma. The conduit may also supply liquid (e.g. saline) for injectioncapability during use as an electrosurgical instrument.

For example, the gas and/or saline could be introduced along the innerconductor of the coaxial feed line in a manner similar to theembodiments shown in FIGS. 10 and 11, to be injectable out of anaperture formed in the probe tip 292. Alternatively a separate gasconduit may be mounted alongside the coaxial feed line.

An alternative embodiment of a probe tip which is suitable forelectrosurgery in addition to instrument channel sterilization is shownin FIG. 13. The probe tip 402 comprises a dielectric block 416 that haslayers of metallization on its upper and lower surfaces. The innerconductor 418 of the coaxial cable 406 protrudes from the distal end ofthe coaxial cable 406 and is electrically bonded (e.g. using solder) tothe upper layer of metallization (first electrode). The outer conductorof the coaxial cable 406 is electrically coupled to the lower layer ofmetallization (second electrode) by a braid termination 420. The braidtermination 420 comprises a tubular part that is electrically bonded tothe outer conductor and a distally extending plate part that fits underthe dielectric block 416 and is electrically connected to the lowerlayer of metallization.

In this embodiment, a shaped piece of dielectric material 422 isattached to the lower surface of the dielectric block 416. It may besecured to the lower layer of metallization. The shaped piece ofdielectric material 422 is curved such that in cross-section its lowersurface describes the chord of a circle between the edges of thedielectric block 416. In the longitudinal direction, the shaped piece ofdielectric material 422 comprises a proximal part with a constantcross-section and a distal part in which the underside gradually tapers(e.g. in a curved manner) towards the dielectric block 416.

In this embodiment, the gas conduit 408 terminates with a needle 424(e.g. a hypodermic needle) which has an outer diameter smaller than thegas conduit 408 and which terminates with a sharp point. The needle 424is retained in a longitudinal bore hole 426 through the shaped piece ofdielectric material 422. Longitudinal movement of the gas conduit 408relative to the dielectric block 416 acts to extend and retract theneedle 424 from the probe tip.

A cross-section through the withdrawal device 20 positioned on thehandle of a scoping device 50 is shown in FIG. 14. The withdrawal device20 is able to withdraw a coaxial cable 12 from an instrument channel 54,in a direction shown by arrows 18, at a predetermined rate. Thewithdrawal device 20 comprises a housing 21 containing a motor (notshown) and two rollers 25, wherein the motor acts to rotate rollers 25via cogs 23, 24. The first cog 23 may be directly powered by the motor,and transfers rotational movement to the rollers 25 through a second cog24 on each roller. The coaxial cable 12 is gripped between the rollers25 such that it is withdrawn from the instrument channel 54 as therollers 25 rotate.

The withdrawal device 20 is releasably attached to the scoping device 50by an attachment portion 26. By attaching the withdrawal device 20directly to the scoping device 50, it is ensured that the rotation ofthe rollers 25 acts to withdraw the coaxial cable 12 rather than movethe device body along the cable. The withdrawal device 20 can thereforebe set up to withdraw the coaxial cable without further user interactionduring the process.

The withdrawal device 20 can also be configured to run in a ‘reverse’mode to insert the coaxial cable 12 through the instrument channel 54.The reverse mode may be selected by a user through a switch on thehousing 21 of the device. In addition, the rate of withdrawal orinsertion is set by the speed of the motor. However, the speed of themotor may be adjustable. For example, the motor may comprise a controldevice for setting the speed. This may be adjusted by a control knob onthe housing of the device. In alternative embodiments, the operationmode (forward/reverse) and speed of the motor may be set by amicrocontroller which is part of the control device. The microcontrollermay itself receive inputs from an external processing device, e.g. aRaspberry Pi® or Arduino® device.

FIG. 15 shows a cross-section through the motor 27; cogs 23, 24; rollers25 and instrument cable 12. As can be seen in the figure, the rollers 25have an hourglass cross-sectional shape which gives a good fit betweenthe rollers and the instrument cable, increasing friction to ensure thatthe coaxial cable 12 is smoothly pulled by rotation of the rollers 25.The rollers 25 may be made of a silicone material which conforms to thesurface shape of the coaxial cable 12. In addition, the rollers 25 arebiased towards each other, in a direction shown by arrows 28, to ensuregood contact between the rollers 25 and the surface of the coaxial cable12.

FIG. 16 shows a view of an alternative embodiment of a withdrawal device20. In this embodiment, the withdrawal device 20 further comprises adrum 22 around which the coaxial cable 12 is wrapped as it is withdrawnfrom the instrument channel of a scoping device. The drum 22 may have aspring drive mechanism to automatically wind the coaxial cable 12 aboutthe drum as it is withdrawn by action of the rollers 25. Gas and RFand/or microwave EM energy are provided to the coaxial cable 12 via aconnecting tube 42 and a connecting wire 32, which may respectively beconnected to a gas supply and a generator (not shown). These connectionsmean that the probe tip at the distal end of the coaxial cable 12 isable to carry out sterilization of the instrument channel as it iswithdrawn by the withdrawal device 20.

The drum 22 may also be used to store the coaxial cable 12 before itinserted into an instrument channel by the same motor and rollermechanism discussed above. The drum and housing may provide a sterileenvironment, as well as providing a space saving storage place for thecable 12.

FIGS. 17A-17C show a sterilization apparatus in use for sterilizing theinstrument channel of a scoping device 50. In FIG. 17A, the scopingdevice 50 is hung from a stand 60 so that the insertion tube 52 hangsvertically downwards. The coaxial cable 12 of an elongate sterilizationinstrument is fully inserted in the instrument channel within theinsertion tube. A withdrawal device 20 is attached to the scoping device50, and is positioned on the coaxial cable 12 towards its proximal end.A generator 30 is configured to provide RF and/or microwave frequency EMradiation to the elongate instrument via connecting wire 32. A gassupply 40 is configured to supply a gas, e.g. Argon, to the elongateinstrument via a connecting tube 42.

In FIG. 17B, the motor of the withdrawal device 20 has been switched onto withdraw the coaxial cable 12 from the instrument channel of thescoping device 50 at a predetermined rate. At the same time, a probe tip(not shown) at the distal end of the coaxial cable 12 is generating anon-thermal plasma to sterilize the instrument channel. The plasma isgenerated at the probe tip by producing an electric field from thereceived RF and/or microwave frequency EM energy across a flow path ofgas received from the gas supply 40. The gas reaches the probe tipthrough a gas conduit which extends the length of the elongateinstrument.

FIG. 17C shows the apparatus when the coaxial cable 12 has beencompletely withdrawn from the instrument channel. At this point theinstrument channel is completely sterilised, requiring no furtherprocessing such as rinsing. The coaxial cable 12 and insertion tube 52both hang vertically downwards from the stand 60, which avoidscontamination by contact with other surfaces. The withdrawal device 20remains attached to the scoping device 50. The generator 30 and gassupply 40 can be switched off as there is no further need for plasma tobe produced at the probe tip.

FIG. 18 shows a plan view of a probe tip 600, suitable for sterilizationof an instrument channel, connected to the distal end of a coaxial cable610. The probe tip is configured to produce a circumferential jet ofthermal or non-thermal plasma which can be directed at the wall of theinstrument channel as the elongate instrument is withdrawn. In thisembodiment, the first electrode 602 is a circular plate of conductingmaterial, such as copper, which is connected to the inner conductor ofthe coaxial cable 610. The second electrode 604 is a cylinder ofconducting material, e.g. copper, connected to the outer conductor ofthe coaxial cable 610. Between the second electrode 604 and the innerconductor there is a dielectric element, wherein the first electrode 602is mounted on the end of the dielectric element. There is an annularopening between the first and second electrodes which defines the end ofthe gas conduit and out of which a thermal or non-thermal plasma isemitted when in use. The elongate instrument comprises a sleeve (notshown) which surrounds the coaxial cable from a proximal to a distal endof the instrument so as to define a gas conduit between the sleeve andthe outer surface of the coaxial cable 610. FIG. 19 shows an end view ofthe probe tip 600 of FIG. 18 with the first electrode 602 removed. Ascan be seen in FIG. 19, the dielectric element 606 is positioned betweenthe second electrode 604 and the inner conductor 612 of the coaxialcable 610. There are a number of groove 608 in the outer surface of thedielectric element 606 where gas is subjected to an electric field toproduce a thermal or non-thermal plasma which is then emitted from theprobe tip 600. The equally spaced grooves 608 help ensure that theplasma is emitted circumferentially and directed at the walls of theinstrument channel. The dielectric element 606 may be elongate such thatit has a length substantially equal to that of the second electrode 604.

1. A sterilization apparatus for sterilizing an instrument channel of asurgical scoping device, the apparatus comprising: a sterilizationinstrument configured to be inserted through the instrument channel of asurgical scoping device, the sterilization instrument comprising: anelongate probe comprising a coaxial cable for conveying radiofrequency(RF) electromagnetic (EM) energy and/or microwave EM energy, and a probetip connected at the distal end of the coaxial cable for receiving theRF and/or microwave energy, wherein the coaxial cable comprises an innerconductor, an outer conductor and a dielectric material separating theinner conductor from the outer conductor, wherein the probe tipcomprises a first electrode connected to the inner conductor of thecoaxial cable and a second electrode connected to the outer conductor ofthe coaxial cable, and wherein the first electrode and second electrodeare arranged to produce an electric field from the received RF and/ormicrowave frequency EM energy; and a withdrawal device for withdrawingthe sterilization instrument from the instrument channel at apredetermined rate.
 2. A sterilization apparatus according to claim 1,wherein the sterilization instrument is further configured to beextendable out of the instrument channel to deliver the RF EM energyand/or the microwave EM energy into biological tissue located at adistal end of the instrument channel.
 3. A sterilization apparatusaccording to claim 1, wherein the sterilization instrument furthercomprises a gas conduit for conveying gas to the probe tip, and whereinthe first electrode and second electrode are arranged to produce anelectric field from the received RF and/or microwave frequency EM energyacross a flow path of gas received from the gas conduit to produce athermal plasma or a non-thermal plasma.
 4. A sterilization apparatusaccording to claim 3, wherein the coaxial cable has a lumen extendingfrom a proximal end to a distal end of the cable, wherein the lumenforms the gas conduit for conveying gas through the elongate probe tothe probe tip.
 5. A sterilization apparatus according to claim 3,wherein the gas conduit passes through the probe tip.
 6. A sterilizationapparatus according to claim 3, wherein the probe tip is a plasmaapplicator having an enclosed plasma generating region and an outlet fordirecting plasma out of the plasma generating region towards an innersurface of the instrument channel.
 7. A sterilization apparatusaccording to claim 3, wherein the coaxial cable comprises a layeredstructure comprising: an innermost insulating layer; an inner conductivelayer formed on the innermost insulating layer; an outer conductivelayer formed coaxially with the inner conductive layer; and a dielectriclayer separating the inner conductive layer and the outer conductivelayer, wherein the inner conductive layer, the outer conductive layerand the dielectric layer form a transmission line for conveying RFand/or microwave frequency energy, and wherein the innermost insulatinglayer is hollow, thereby providing a longitudinal channel within thecoaxial cable.
 8. A sterilization apparatus according to claim 7,wherein the coaxial cable further comprises a first terminal that iselectrically connected to the inner conductive layer and which extendsthrough the innermost insulating layer into the channel; and a secondterminal that is electrically connected to the outer conductive layerand which extends through the dielectric layer and innermost insulatinglayer into the channel; wherein the first terminal and the secondterminal may be arranged to form electrical connection with the firstand second electrodes on the probe tip, wherein the probe tip isinsertable in or through the longitudinal channel.
 9. A sterilizationapparatus according to claim 7, wherein the probe tip comprises: anextension of the innermost insulating layer of the coaxial cable; thefirst electrode, comprising an extension of the inner conductive layerof the coaxial cable; a dielectric cylinder placed over the innerconductive layer; and the second electrode, comprising a metal tubewhich is electrically connected to the outer conductive layer of thecoaxial cable.
 10. A sterilization apparatus according to claim 9,wherein the dielectric cylinder comprises a number of holes in the wallsof the cylinder.
 11. A sterilization apparatus according to claim 7,wherein the longitudinal channel comprises or contains the gas conduit.12. A sterilization apparatus according to claim 1, wherein the probetip comprises a single piece of metallized dielectric material.
 13. Asterilization apparatus according to claim 1, wherein the probe tip hasa parallel plate structure comprising: a substantially planar body ofdielectric material; a first conductive layer on a first surface of theplanar body as the first electrode; and a second conductive layer on asecond surface of the planar body that is opposite to the first surface,as the second electrode.
 14. A sterilization apparatus according toclaim 1 further comprising: a container defining a sterilizationenclosure for the surgical scoping device, and a plasma generating unitfor creating a non-thermal plasma or a thermal plasma within thesterilization enclosure for sterilizing an exterior surface of thesurgical scoping device, wherein the container includes a chamber forreceiving a control head of the surgical scoping device, and wherein theplasma generating unit includes an annular body for enclosing aninstrument tube of the surgical scoping device.
 15. A sterilizationapparatus according to claim 1, wherein the probe tip further comprisesa cleaning brush.
 16. A sterilization apparatus according to claim 1,wherein the predetermined rate is less than 10 mm per second.
 17. Asterilization apparatus according to claim 1, wherein the withdrawaldevice comprises: a cable coupling element operably connected to theelongate probe at a proximal end thereof; and a motor arranged to drivethe cable coupling element to cause relative movement between theelongate probe and the instrument channel in a longitudinal direction.18. A sterilization apparatus according to claim 17, wherein the cablecoupling element comprises a plurality of rollers defining a spacebetween them for receiving the elongate probe, the rollers beingarranged to grip an exterior surface of the elongate probe wherebyrotation of the rollers causes longitudinal movement of the elongateprobe.
 19. A sterilization apparatus according to claim 18, wherein themotor is disengagable from the cable coupling element.
 20. A probewithdrawal device for moving an elongate probe through an instrumentchannel of a surgical scoping device, the probe withdrawal devicecomprising: a cable coupling element operably connected to the elongateprobe at a proximal end thereof; and a motor arranged to drive the cablecoupling element to cause relative movement at a predetermined ratebetween the elongate probe and the instrument channel in a longitudinaldirection.